Hi GuysI am trying to figure out exactly how Exchange 2003 interacts with AD.Let's say I my domain is usa.company.com, part of the company.com forest, and I have two Exchange 2003 servers per domain (exch1 and exch2.usa.company.com) and 4 DC's per domain (dc1.usa.company.com etc). The GC is DC4.usa.company.comAn Outlook client, whose mailbox is on Exch2.usa.company.com, wants to send an email to User2 in the Japan domain.From what I understand this is the process:Exch2 selects a GC and DC's to connect to via the DSAccess process.Outlook connects to Exch2Exch2 carried out GAL/GC lookups for Outlook using the DSProxy processWhen Outlook sends an email, it gets sent to the Store.exe process on Exch2 and then finally the Categorizer process which is responsible for querying AD for message delivery- it queries AD using the DSAccess process (but there is also a DSAccess cache on each Exchange server to prevent unncessary lookups)Am I correct here?

Everything is perfect, except one thing... "Exch2 carried out GAL/GC lookups for Outlook using the DSProxy process" -> Here outlook client connected to corporate network does the GAL lookup through DSProxy process but it is just for redirection for the first time to nearby GC then actual lookup will be done by GC and then after all lookup requests go directly to GC refered by DSProxy first time, lookup will be done thorough Name Service Provider Interface [NSPI] supported by GC only (not DC) for Microsoft clients... Amit Tank | MVP Exchange Server | MCITP: EMA | MCSA: M | http://ExchangeShare.WordPress.com

Hi Amit,""Exch2 carried out GAL/GC lookups for Outlook using the DSProxy process" -> Here outlook client connected to corporate network does the GAL lookup through DSProxy process but it is just for redirection for the first time to nearby GC then actual lookup will be done by GC and then after all lookup requests go directly to GC refered by DSProxy first time, lookup will be done thorough Name Service Provider Interface [NSPI] supported by GC only (not DC) for Microsoft clients... "So you are saying after the first DSProxy referall to a GC, Outlook opens a direct connection to that GC and, from then on, that GC does all the searches? Is there any name for this process, and what protoool does this use? And how does whether the client is in Outlook cached (i.e. uses the OAB) or online with Exchange mode affect GC referrals?Also, when the message gets to Exchange (Categorizer) and Exchange needs to locate the home Exchange server/ home mailbox Store of the recipient, what is the name of the process whereby Exchange queries AD for this information? Is it DSAccess or NSPI...I'm a little confused by that? Is DSAccess just the process of intially locating DC's/GC, or it also the process of Exchange querying them from then on for recipient information?Thanks!

Yes, DSProxy refer the lookups to GC directly and works on NSPI RCP call from outlook to directly nearest GC. Michael has explained oultook client lookup very well in below article. Exchange, Active Directory, and WINS http://theessentialexchange.com/blogs/michael/archive/2008/01/16/exchange-active-directory-and-wins.aspx About second Q, Yes, Exchange relay on categorizer for maildelivery. Categorizer is a component of Exchange which is used to send a mail to proper destination so when a mail sent, categorizer queries to DSAccesscomponentto locate AD Server list and if recipient info can't be found in DSAccess Cache then categorizer opens directly a LDAP connection to GC for furtherinformationand mail send. NSPI is just for outlook client lookups not for categorizer process.Amit Tank | MVP Exchange Server | MCITP: EMA | MCSA: M | http://ExchangeShare.WordPress.com